DESCRIPTION (Adapted from the applicant's specific aims): Transcription factors play important roles in controlling development in response to cellular or external signals in all organisms. A subfamily of b-zipper proteins has been identified from Arabidopsis, resulted from a previous investigation of the nuclear factor which binds to a plant viral promoter element. Arabidopsis have about seven members of this group of b-zipper factors and their functional roles are currently unknown. In this project, methods will be developed for a gene disruption protocol to knockout each of the individual genes and to reveal functional roles through examining the phenotypic defects of those gene disruption lines. During this funding period, two different members of this gene family, TGA2 and TGA3, will be chosen as targets for the gene disruption study since genomic clones for these loci have already been obtained. The lab have shown the feasibility of gene disruption in plant cell culture system, and is in the process of optimizing and adapting into whole plant level. The success of this study will not only elucidate the roles for these two members of this particular b-zipper family of plant transcription factor, it will also open the way for targeted gene disruption analysis of other interesting genes in higher plants. This is a high risk but high reward research effort.